What do Apple ( AAPL), Starbucks ( SBUX) and Facebook have in common? They're brands that are the definition of cool. But in a recession, does being hip still sell? You bet. "Cool always sells because the basis of cool is aspirational," says Del Breckenfeld, author of The Cool Factor: Building Your Brand's Image Through Partnership Marketing (Wiley). "People aspire to be like the actors, musicians or celebrities that society deems as cool." Here are eight reasons why it's good to be in vogue and how to do it right: Fabulous differentiator: Find a way to set yourself apart from the competition. You don't necessarily need a ton of cash to do so. Just get yourself noticed by those who shape opinions in your niche. That could be bloggers, teens and tweens. It could be friends you think are cool. LivingSocial has grown to 7 million users in two years by allowing people to review and share with their pals what they think is cool, from books to beer. "No one wants to be picked last in gym class," says CEO and co-founder Tim O'Shaughnessy. "So if you see someone who is perceived by others as being the first picked in gym class, you mold yourself after them. It's human nature." By building this network, LivingSocial has been able to help companies like book publishers find out what people are reading and recommending. And thanks to a relationship with Amazon.com ( AMZN), it can even track sales. It's a state of mind: Cool can mean different things to different audiences. For example, Best Buy's ( BBY) Geek Squad makes it cool to be a geek, says Dr. Scott Testa, professor of marketing at St. Joseph's University who also writes Dr. Scott's Cool Marketing and Business Blog. Mountain Dew's close relationship with extreme sports makes it the brand for teen boys, but Cadillac's coolness is more mature and sophisticated. So consider your audience when determining how cool you want to be.